1. Field of the Invention
The present invention relates to a refrigerant evaporator that includes a plurality of laminated tubes constructed from a pair of metal plates to perform a heat exchange between a liquid-gas phase refrigerant introduced from a pressure reducing means and an air flowing outside thereof.
2. Description of Related Art
A refrigerant evaporator 100 having a refrigerant route shown in FIG. 7 is disclosed in Japanese Patent Application No. 8-182307.
The evaporator 100 is constructed from a plurality of tubes and corrugate fins 104 that are laminated in an alternating pattern. In each tube, an air downstream side refrigerant passage 102 and an air upstream side refrigerant passage 103 are formed. Here, an arrow denotes an air flow direction. At both upper and lower ends of the air downstream side refrigerant passage 102, an upper tank portion 106 and a lower tank portion 108 are provided. At both upper and lower ends of the air upstream side refrigerant passage 103, an upper tank portion 105 pipe 109 is connected to the lower tank portion 108, which is disposed at the air downstream side. A refrigerant outlet pipe 110 is connected to the upper tank portion 105, which is disposed at the air upstream side. The refrigerant flows inside the evaporator 100 in accordance with the flowing route: "refrigerant inlet pipe 109.fwdarw.lower tank portion 108.fwdarw.air downstream side refrigerant passage 102.fwdarw.upper tank portion 106 .fwdarw.air downstream side refrigerant passage 102.fwdarw.upper tank portion 105.fwdarw.air upstream side refrigerant passage 103.fwdarw.lower tank portion 107.fwdarw.air upstream side refrigerant passage 103.fwdarw.upper tank portion 105.fwdarw.refrigerant outlet pipe 110".
In the evaporator 100, the liquid phase refrigerant flows in the upper tank portions 105 and 106 in one direction and is distributed into each air downstream side refrigerant passage 102 and air upstream side refrigerant passage 103 by the gravitational force. Thus, the liquid phase refrigerant tends to either flow into the refrigerant passages 102 and 103 disposed at the upstream side of the refrigerant flow, or not to flow into the refrigerant passages 102 and 103 disposed at the downstream side of the refrigerant flow. Also, the refrigerant flowing in the lower tank portions 107 and 108 is distributed into the each refrigerant passage 102 and 103 and flows up inside thereof. The refrigerant flows up inside the refrigerant passages 102 and 103 after it flows inside the lower tank portions 107 and 108 into the downstream side of the refrigerant flow. Thus, the refrigerant tends to flow into the refrigerant passages 102 and 103 disposed at the downstream side of the refrigerant flow with being influenced by the inertia force.
For example, in the evaporator 100, as shown in FIG. 9, the refrigerant flowing in the lower tank portion 107 tends to flow into the refrigerant passages 103a disposed at the downstream side of the refrigerant flow, or in the vicinity of the refrigerant outlet pipe 110. That is, an excess amount of refrigerant flows into these refrigerant passages 103a. The liquid phase refrigerant cannot be evaporated completely and super-heated in these refrigerant passages 103a. Therefore, the temperature of the refrigerant at the outlet of the evaporator 100 becomes low, and a temperature responsive expansion valve decreases the amount of the refrigerant flowing into the evaporator 100. Consequently, the cooling ability of the evaporator 100 becomes reduced.